Amplifying system



June 28, 1938. l L; K. SWART AMPLIFYING SYSTEM Filed July 8', 1936 lNVE-NTOR Z.E Saudi/1f BY l Wc x ATTORNEY Patented J une 28,y 1938 v"AMPLIFYING SYSTEM Leland Kasson Swart,.Moimtan`Lakes,vll}l.J.,r assignorto American Telephone and'l'elegrapli y Company, a corporation `-of7 NewioijklrV 'fgl Application July s, 1936; serial1 No. 89,623

9 claims.j (01.".179-171) This invention relates to amplifying systems. More particularly, this invention relates to amplifying systems employing a gas tube as the amplifying element. Y

This invention is applicable, among other yuses,

to telephony, for the purpose of obtaining in an `outgoing or outputV circuit `an amplication of` voice currents originating in an incoming or input circuit. Itis also applicable to telegraphy and- 10 signaling systems generally, and where ampli-- iication is necessary, as for example, for receiving, recording, and for reproducing impulses of 1 electrical energy. 1 c j In the tube of this invention a gas such as neon,

argon, helium or krypton, or any combination of usl'uch ygases and nitrogen at low pressurefis ern-` 'ployed. The tube includes three or Vmore electrodes, two of vwhich are connected to the input or incoming circuit and a` third electrode and ".20 Vone of the other electrodes are connected or cou-y pled to an outgoing or output circuit. A It is a prop-A Y erty of a tube of this type to exhibitk a high impedance between anytwo of the electrodes when the 4gas is in a deionized condition. `When the' '25 gas of the tube becomes ionized, however, the

.35 ionized according to the application'of such currents to the inputcircuit of the tube and regularly deionized at avery high speed, that is, at a frequency well above that of audibility. In 4'the output circuit of thetube will be found highly 40 l"ampliiied'current or currents. n

'I'his invention will `be better understood `from 'the detailed description hereinafter following,

when read in connection with the accompanying y drawing, in which Figure l shows the invention applied to ahot cathode type of gas tube in the output circuit of which direct current potential is applied and periodically interrupted at a highs speed; Fig. 2 is a modification of Fig. l in which ,50 they output circuit is energizedvby a high frequency potential; Fig. 3 shows the invention appliedto Va gas-filled tube of the so-called cold cathode type,` the output circuit of vwhich is energized by directcurrent potential interrupted at high frequency.; and Fig. 4 is a modification of Vthe a1,-

lcircuit of a gas-filled:'tube'designated N1.

-rangement1ofrvig-3in which the i'nterrupter is of an electricaltype involving no moving parts.

Referring to Fig. `1"ofthe drawing', a' currentv within the audiblelfrequencyrange or aplurali'ty of vsuch currents or ordinary speech signals may 1:5 be 'appliedthrough 'a transformer r`T1 to the input .The 'input circuit of "the tube includes a grid and cathode and 'theigridpiis normally/.biased irornv a Vsource of direct currentrpotential designatedrBl,

Vwhich'isconnected rin series vwith the secondary Winding of 'thetransformerTlbetween thegrid andcathode'oithetube The'output circuit o'f the `tube is formedby the` cathodeand anodeand includes the-primary winding of "a transals former T2; an interrupter Hand a'source of dil rect currentfpotential B2.'v Thejsecondary wind ling of the .transformer T2 may'` be connect'edto former, .thel otherwinding' ofv which (not shown)` 25 may be connected to an alternating current generator 'of anyl we1l'known';type; The `midpoint l of the winding# connected to the heater may be connected to the cathode'asshown.`

vThe source Bzjwill have'f'a4 terminal-voltage 30 which is less than the `breakdown voltage between 1 the'anode and'cathodeof the .tube N1 but which lis greater'than the-.voltage required to 1sustain` ionization of the gas'between those electrodes. The interruption' of 'this potential-,vat high speed by the interrupter H, whichmay be any `form of circuit breaker; will reduce the voltage 4between the anode and cathode :substantially tofzero,fand y hence deionize the gas of the tube at a frequency correspondingto the frequency of interruption (40 of/the device HI.l 'l

, As' the input voltage within the range orf` ,aude ibility` is applied through transformer 'I-rto ythe grid orvinput -circuit Y of the tubefNi. the gas Y within the tube will become ionized and during 45 ionization a large current will flow Abetween the anode and cathode of thetube aswell as through l the primary winding `of the transformer T2. `A correspondingly large current will iiow through the secondary ,winding of the transformerTz to `5 0 the load or other apparatus connected thereto.

`But the potential Aapplied. to the anode will vsoon be withdrawn by the action of the interrupter H.' When this occurs there will be an absence of current-in both windings of the transformer T2.

ffznzws.

If the input voltage or voltages continue to be appliedto the grid or input circuit of the tube N1, currents will again iow through the windings of the transformer T2 and be interrupted according to the speed of the interrupter I-I. 'Ihe current in the secondary Winding of the transformer T2, however, will closely resemble the input voltage or voltages although it will be a highly amplied current. The high speed interruptions of that current will onlyslightly affect the intelligibility of these amplified currents or the signals carried thereby. It is, therefore, important that the interrupter be of very high speed so as to considerably reduce the effect of the interruptions upon the intelligibility of the signals carried by the'current but at the same` themselves initiate the operation of the circuits.

In Fig. 2 the anode or output circuit of the tube N1 is supplied with current from the generator G of a frequency well above audibility. This generator G may have a peak voltage approximating that of the source B2 of Fig. 1, that is, a Voltage between the breakdown and sustaining voltage values of the tube. A rectifier Y is connected in series with the generator G for permitting only positive potentialr to be applied to the anode of the tube. It will be understood, however, that this rectifier is by no means Vnecessary tothe operation of the circuit and may be entirely eliminated if so desired.

Fig. 3 shows the invention applied to an arrangement including a cold cathode-gas-lled tube N2 ofthe three-electrode type. The at plates or cathodes of this tube are connected to a circuit which includes the secondary winding of the transformer T1 and a source of po- Y tential Ba The anode of the tube is connected to the lower cathode through a circuit which includes the primary winding of the transformer T2, a high frequency interrupter and sources of *potential B3 and B4, as shown. The sources B3 plied between the cathodes of the tube N2y and there will be produced highly amplified currents inthe anode or output circuits of the tube. These Yamplified effects will be transmitted vto the load or other device connected to the secondary Winding of the transformer T2.` These amplified currents, moreover, will be interrupted at the frequency of interruption of the device H. This frequency will be sufficiently high, however, so as not materially to affect the character or intelligibility of the currents or signals thus transmitted and amplified. The interrupter H acts as in Fig. l primarily to remove potential from the anode of the tube N2 so as to denitely deionize the gas of the tube at regular intervals.

Fig. 4 isa modification ofthe arrangement shown in Fig. 3 but in place of theinterrupter H of Fig. 3, a condenser C2 and a resistor R, connected in parallel relationship, are substituted therefor. The condenser and resistor are so chosen that they will effectively interrupt the flow of current in the anode or output circuit of the tube-N2 at regular intervals. This may -be accomplished, for example, as follows:

When the gas of the tube becomes. ionized, the condenser C2 will be charged to a voltage which sufficiently opposes that of the sources B3 and B4 that it will reduce the net effect of these voltages so applied to the anode below the sustaining voltage value of the tube. When the sustaining voltage is no longer applied to the anode of the tube, the gas of the tube will become deionized. The condenser C2 will then discharge through the resistor R to a substantially lower voltage. When a sufciently low voltage at condenser C2 is reached, the voltage on the anode of the tube Ywill be again raised above the voltage required to maintain ionization of the gas within the tube. Condenser Cz will again be charged by current from sources B3 and B4 to a voltage sufficiently high so as again to reduce the effective potential at the anode, below that required for sustained ionization, and so this continues.

While vthis invention has been described in connection with the amplification of applied currents of the audible range of frequencies, the invention is not limited to applications of such This amplifying system may be scribed in certain particular arrangements merelyA for the purpose of illustration, it will be understood that the general principles of this invention may be applied to other and widely varied organizations without departing from the spirit of the invention and the scope of the appended claims.

.What is claimed is:

, l. An amplifying system comprising a gas tube having at least three electrodes, means for simultaneously applying a plurality of voltages of frequencies within the range of audibility to two of the electrodes of the` tube, all of said voltages corresponding to speech signals, an output circuit connected to the third electrode and one of the other electrodes of the tube in which the applied voltages in amplified form are presv ent, and a source of interrupted voltage of a frequency outside the range of audibility, said source being connected in said output circuit for periodically deionizing the gas within the tube.

2. An amplifying system comprising a cold cathode gas tube having two cathodes and an anode, a source of alternating voltages corresponding to speech signals, all of said voltages being applied simultaneously to the two cathodes of the tube, a circuit connected between the anode and one of the cathodes of the tube in which will flow alternating voltages corresponding to the signal voltages applied to the cathodes but considerably amplified, and means for periodically deionizing the gas within the tube, thefrequency of deionization being different from the frequency of the alternating voltages of said source.

3. The combination of a gas-filled tube having input electrodes and output electrodes, a lsource of telephone signals coupled to the input electrodes of the tube, said source emitting a plurality of voltages simultaneously which together have a complex wave form, a source of potential exceeding the sustaining voltage of the tube and connected between the output electrodes of the tube, means for interrupting the flow of current in the output circuit of the tube at a frequency greater than any frequencyv contained'within the telephone signals of the source, and means for translating the amplied currents of the output circuit of the tube. v

4. The combination of a gas tube having three electrodes, a source'of voice frequency signals corresponding to ordinary speech transmitted over a circuit coupled to two of the electrodes of the tube, a source of periodically interrupted potential connected between the third electrode and one of the other electrodes of the tube, the peak voltage of said latter source exceeding the sustaining voltage of the tube, the impedance in the circuit of the third electrode periodically varying from a high value to a negligible value, thisv voltage variation being comparable with the degree of amplification of the Voice frequency signals, and means for utilizing the amplied signals.

5. An amplifying system comprising a gas tube having at least three electrodes, a source of voice frequency signals corresponding to ordinary speech, a transformer coupling said source to a circuit including two of the electrodes of the tube so as to simultaneously apply to said two electrodes substantially all of the components of said 130' signals, a circuit interconnecting the third electrode and `one of the other electrodes of the tube, the latter circuit including a source of potential exceeding the breakdown voltage of the gas Withirf' quencies, and a load circuit coupled to the output circuit of the tube.

7. A telephone amplier comprising a gas-lled tube having at least three electrodes forming ini put and output circuits, a source of telephone speech signals coupled to the input circuit, and a source of voltage connected to the output circuit, said latter source being interrupted at a rate such that the interrupted time will be greater than the deionization time of the gas of the tube, the magnitude of the voltage of said latter source CFI being less than that required to initiate ionization of the gas of the tube but greater than that required to sustain ionization after it is initiated.

8. A telephone amplier comprising a gas-filled tube having at least three electrodes forming input and output circuits for the tube, a source'of telephone signals coupled to the input circuit, a circuit coupled to the output circuit forreceiving the amplified signals, said input circuit including means responsive to said telephone signals to ionize the gas between the input electrodes of the tubeduring the application of said signals, and means independent of said telephone signals for periodically deionizing the gas between the outvoltage connected between the third electrode and one of the other electrodes, the voltage of said y source being not greater than the voltage required to initiate ionization of the gas between the two last mentioned electrodes but greater than that required to sustain ionization after it is initiated, means for periodically interrupting the voltage of said source, and means for observing said amplified frequencies.

.LELAND KASSON SWART. 

